The present invention relates to a connecting structure between a resin tube and a tubular mating member. The present invention relates to, in detail, a connecting structure between a resin tube, such as an automotive tube such as, for example, a fuel tube, and a tubular mating member such as a metal pipe.
A rubber tube has been conventionally used as an automotive fuel tube or the like. In recent years, however, the rubber tube tends to be replaced by a resin tube made of hard resin, such as nylon, having good gasoline permeability resistance or the like due to its lower cost. The same thing occurs to other automotive dedicated tubes such as an air tube.
Conventionally, as disclosed in, for example, U.S. Pat. No. 5,161,833 and U.S. Pat. No. 4,991,882, in case of fluid-tight connecting a resin tube of this type to a mating member, the following connecting structure is known. A containing portion is formed such that a retaining member is retained on axial one end of an axis bore of the cylindrical housing and a ring-shaped elastic seal member, such as an O ring, is retained axially inward of this retaining member. When the insertion end portion of a tubular mating member is inserted into the interior of the retaining member from one end of the housing thereof, the retaining member is snap-engaged with an annular stopper on the insertion end portion to thereby fluid-tight connect the mating member to the one end portion of the housing. At the same time, an engaged one end portion having an outer peripheral surface smaller in diameter than the one end portion is formed integrally with the other end of the housing. The inner peripheral surface of the one end portion of the resin tube is press-fitted into the engaged end portion and the resin tube is fluid-tight connected to the other end portion of the housing. The housing having the retaining member retained on one end portion and the tubular mating member inserted into the one end portion of the housing form a quick connector as a whole. Normally, a tube connecting structure using the quick connector is widely used.
The above-stated quick connector is complicate in structure and expensive. Due to this, there has been proposed a method of directly connecting a resin tube to a tubular mating member not using the quick connector but using a simple member. This is disclosed in, for example, the published specification of EP0840051. Specifically, it discloses a hose connecting structure in which the first engagement portion of a tubular mating member is formed integrally with the end portion, which is blow-molded, of a resin tube, an elastic seal member such as an O ring is installed into an annular groove, which is also blow-molded, and the second engagement portion of the tubular mating member is engaged with the first engagement portion of the resin tube, thereby connecting the resin tube with the tubular mating member.
In the tube connecting structure connecting a resin tube with a tubular mating member using the conventional quick connector, the engaged end portion of a cylindrical housing is press-fitted into the inner peripheral surface of one end of the resin tube. The problem with this structure is that the connecting portion is lacking in the reliability in terms of pulling resistance and sealing property. And the tube connecting structure using the conventional quick connector is complicated in structure and requires a number of parts. As a result, the structure becomes expensive. It also requires two liquid-tight seal connecting portions axially separated from each other, with the result that the tube connecting structure becomes longer in axial direction. In these circumstances, demand for a tube connecting structure which is more compact, requires lower cost and ensures that a resin tube is liquid-tight connected to a tubular mating member is rising.
By the way, the tube connecting structure proposed in the published specification of EP0840051 as stated above does not employ a conventional quick connector mentioned above. Thus, it is relatively simple in structure and is excellent is sealing property. This is because the resin tube is directly connected to the tubular mating member by putting an elastic seal member between the resin tube and the tubular mating member.
However, due to the fact that the first engagement portion is formed integrally with the end portion of the resin tube so as to engage the resin tube with the tubular mating member, the structure of EP0840051 requires bothersome blow molding. That is, it requires setting a resin tube into a blow molding die and then blow molding or injection molding the first engagement portion, or setting the first engagement portion, which has been molded independently in advance, into a blow molding die and then extruding parison into the blow molding die to thereby blow-molding the first engagement portion. Thus, the structure is disadvantageous in that it has poor productivity and that the merit of low cost is thereby lost.
In view of these circumferences of the prior art, the objective of the present invention is to provide a connecting structure capable of directly connecting a resin tube and a tubular mating member in a fluid-tight condition, unlike a conventional case of using a quick connector where a nipple formed on the other end of the connector housing is press-fitted into an inner peripheral surface of the end portion of a resin tube to make a connection between the resin tube and the mating member, and unlike a conventional case of employing a blow molding for integrally forming a first engaging portion into the resin tube, and thereby providing a connecting structure which is capable of connecting a resin tube and an mating member to each other via an elastic sealing member and which is excellent in sealing properties as well as being a simple and compact in structure and low at cost.
For achieving the above objective, the present invention provides a connecting structure for connecting a resin tube to an mating member in a fluid-tight condition, includes: the resin tube including a tube body formed with a cylindrical wall with a substantially uniform thickness, and a diameter-enlarged end portion which has an opening and is formed at one end of the tube body; a connecting member including a tubular base portion inserted to an outer peripheral surface at the other side of the diameter-enlarged end portion of the resin tube, and a first engaging element extending outward from the base portion; a tubular press-fitting means for preventing the connecting member from removing toward the one end of the resin tube, including at least one press-fitting body press-fitted into the opening of the resin tube from the one end side thereof, the one press-fitting body including an outwardly protruding annular element in a radial direction beyond the outer peripheral surface of the diameter-enlarged end portion at one end side thereof, the at least one press-fitting body being press-fitted into the one end of the resin tube to form the diameter-enlarged end portion, and the inner peripheral surface of the base portion of the connecting member which is inserted and fitted to the outer periphery at the other end side being capable of being firmly attached and fitted or engaged with the other side of the diameter-enlarged end portion in a resisting relation; an annular sealing member mounted in either one of annular grooves of an annular outer peripheral groove formed in a space on the outer peripheral surface of the diameter-enlarged end portion in an axial direction between the annular stopper surface of the bush and the base portion of the connecting member, or an annular inner peripheral groove formed in a space at an inner peripheral of the opening of the enlarged-diameter end portion between the one press-fitting body and the other press-fitting body independent from the one press-fitting body; a tubular mating member including an inserting end portion capable of being relatively inserted into the outer peripheries of the annual stopper surface of the bush and the base portion of the connecting member by being engaged with the outer periphery of the sealing member in a fluid-tight condition, or capable of relatively being inserted into the inner surfaces of the one press-fitting body and the other press-fitting body by being engaged with the inner periphery of the sealing member in a fluid-tight condition; and a second engaging element projecting outward from the outer peripheral surface of the inserting end portion of the mating member in a radial direction, the second engaging element capable of being engaged with the first engaging element when the inserting end portion is relatively inserted into the diameter-enlarged end portion.
In a preferable embodiment of the connecting structure of the present invention, the connecting member has a restricting inner peripheral surface at the other end of the tubular base portion of the connecting member, and the diameter of the restricting inner surface gradually decreases toward the other side of the resin tube. The tubular press-fitting means includes a press-fitting body, and the press-fitting body is press-fitted into one end of the resin tube to form a diameter-enlarged end portion. The diameter-enlarged end portion has a tapered shoulder wall at the other side thereof, and the diameter of the shoulder gradually decreases toward the other side of the resin tube. When the connecting member is inserted and mounted on the outer periphery at the other side, the restricting inner peripheral surface of the base portion of the connecting member is firmly attached and fixed or engaged in a resisting relation with the shoulder wall formed at the other side of the diameter-enlarged end portion of the resin tube. With this arrangement, the movement of the connecting member toward one end of the resin tube is prevented.
The press-fitting means includes one press-fitting body. The press-fitting body includes a protruding element with a stopper surface formed by a flange or cap-shaped holder.
On the outer peripheral surface of the diameter-enlarged end portion of the resin tube, the base portion of the connecting member has an opposing end portion in an opposing relation to the annular back surface of the flange of the press-fitting member. An annular outer peripheral groove is formed in the space in an axial direction between the annular back surface of the flange and end surface of the opposing end portion of the connecting member. In the annular groove, the annular sealing member is mounted in such a manner that the sealing member is in tightly contact with the outer peripheral surface of the diameter-enlarged end portion.
In another embodiment of the connecting structure of the present invention, the press-fitting means includes a first press-fitting member and a second press-fitting member which are independent from each other. The first press-fitting member has a tapered portion at the other end side of the resin tube, and the tapered portion is formed with a tapered outer surface with a diameter gradually decreasing toward the other end side. The second press-fitting member has a flange at one end side projecting from the outer peripheral surface of its tubular press-fitting body. The second press-fitting member is disposed at a position coaxially remote from one terminal end the first press-fitting member.
In a preferable embodiment, the first press-fitting member and the second press-fitting member are integrally formed into one-piece unit.
The resin mating member has an inserting end portion at its one end, and the inserting end portion has a diameter larger than the other end side via a tapered wall portion. When the inserting end portion is inserted relatively into the diameter-enlarged end portion of the resin tube, the inner peripheral surface of the inserting end portion is engaged with the outer peripheral surface of the annular sealing member, and at the same time, the tapered outer peripheral surface of the flange of the press-fitting member is brought into contact with the tapered wall portion of the mating member. On the outer peripheral surface of the inserting end portion of the mating member, an annular second engaging element is formed. The second engaging element is snappedly engaged with the first engaging element of the connecting member when the outer peripheral surface of the flange is brought into contact with the tapered wall.
According to the present invention, the connecting structure which has excellent sealing properties can be provided, wherein the resin tube can be directly connected to the tubular mating member via a tubular or ring-shaped elastic sealing member by use of a connecting member inserted and fixed to the outer peripheral surface of the end portion of the resin tube.
The connecting structure of the present invention does not use a conventional connector having a complicated structure with a nipple to be press-fitted into an inner peripheral surface of the resin tube for connection. The connecting structure does not need the blow molding and blow molding die for integrally forming the first engaging portion and the resin tube into one-piece unit. Thus-formed connecting structure has a simple structure with high productivity and is low at cost.